feat: add startup launch support (#1421)

Add launch-at-startup support across the Electron desktop app and the web CLI.

Electron now supports macOS launch-at-login through the native login item API. Login launches start OpenChamber in the background without opening a window, while Dock activation, deep links, and second-instance launches still open or focus the normal app window. The desktop Settings UI now exposes a localized launch-at-login toggle in Desktop Network Access.

The web CLI now includes `openchamber startup status|enable|disable`, backed by native user services:
- macOS: launchd LaunchAgent
- Linux: systemd --user service
- Windows: Task Scheduler

Startup services run `openchamber serve --foreground` so the OS service manager owns process lifetime and restarts. Foreground service updates now defer restarts to the service manager instead of spawning duplicate CLI restarts.

Startup services snapshot useful environment variables by default so provider tokens, PATH, SSH agent settings, and OpenCode configuration survive login/reboot starts. The snapshot avoids shell/session-only state, uses systemd-compatible env quoting on Linux, and avoids unused env artifacts on macOS.

Also adds localized docs for startup services and environment variables.

packages/ui/src/lib/i18n/messages/ko.settings.ts

@@ -725,6 +725,9 @@ export const settingsDict = {
   'settings.openchamber.sessionRetention.toast.failedArchiveCount': '세션 {count}개를 보관하지 못했습니다',
   'settings.openchamber.sessionRetention.toast.failedDeleteCount': '세션 {count}개를 삭제하지 못했습니다',
   'settings.openchamber.desktopNetwork.title': 'Desktop 네트워크 접속',
+  'settings.openchamber.desktopNetwork.field.launchAtLoginAria': '로그인 시 OpenChamber 시작',
+  'settings.openchamber.desktopNetwork.field.launchAtLogin': '로그인 시 OpenChamber 시작',
+  'settings.openchamber.desktopNetwork.field.launchAtLoginDescription': '창을 열지 않고 백그라운드에서 앱을 시작합니다. Dock 아이콘을 클릭하면 열립니다.',
   'settings.openchamber.desktopNetwork.field.allowLanAccessAria': 'desktop sidecar에 LAN 접속 허용',
   'settings.openchamber.desktopNetwork.field.allowLanAccess': '로컬 네트워크의 다른 기기에서 이 앱 열기 허용',
   'settings.openchamber.desktopNetwork.field.allowLanAccessDescription': '휴대폰, 태블릿, Wi-Fi의 다른 컴퓨터에서 열 수 있도록 앱을 다시 시작합니다.',
@@ -738,6 +741,8 @@ export const settingsDict = {
   'settings.openchamber.desktopNetwork.error.loadFailed': 'desktop 설정을 로드하지 못했습니다',
   'settings.openchamber.desktopNetwork.error.saveFailed': 'desktop 설정을 저장하지 못했습니다',
   'settings.openchamber.desktopNetwork.error.savedRestartFailed': '저장했지만 앱을 다시 시작하지 못했습니다',
+  'settings.openchamber.desktopNetwork.error.launchAtLoginUnsupported': '이 시스템에서는 로그인 시 시작을 지원하지 않습니다',
+  'settings.openchamber.desktopNetwork.error.launchAtLoginSaveFailed': '로그인 시 시작 설정을 업데이트하지 못했습니다',
   'settings.openchamber.opencodeCli.title': 'OpenCode CLI',
   'settings.openchamber.opencodeCli.tooltipPrefix': '선택적 절대 경로:',
   'settings.openchamber.opencodeCli.tooltipSuffix': 'binary.',